simple problem - dynamic variables/params in xsl:value-of select

[BURKHARDT, BRIAN (SBCSI)]

below is simplified xsl template which is being called within a JSP that is
giving me the problem - the actual version passes a param from the JSP but
for the sake of the example im using a variable...

using the sample XML, im wanting the template to return "1234" instead of
"msgNo" - is that possible?

xml example: <WISL><msgNo>1234</msgNo></WISL>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
version="1.0">
        <xsl:output method="html"/>
        <xsl:variable name="theTag">msgNo</xsl:variable>
        <xsl:template match="/WISL">
                <xsl:value-of select="$theTag"/>
        </xsl:template>
</xsl:stylesheet>

thanks in advance,
Brian....